have something on good authority

your utmost to please someone by attending to all their needs or requests

The expression originally referred to someone waiting kicking their heels until an important person summoned them or would see them.

1999 - Shyama Perera - I Haven't Stopped Dancing Yet - Tammy and I sat on a vinyl bench seat and watched the visiting flow while Jan disappeared to dance attendance on her mother.

for auld lang syne

for old times’ sake

The phrase literally means for old long since and is the title and refrain of a song by Robert Burns (1788).

under the auspices of

with the help, support or protection of

Auspice (since the late 18th century ! almost always used in the plural) comes from the Latin word auspiciu, which means the act of divination carried out by an auspex in ancient Rome. The auspex observed the flight of birds in order to foretell future events. If the omens were favourable he was seen as the protector of the particular enterprise foretold.

Shortly before his death Robert Burns is reported to have said, 'Don't let the awkward squad fire over me'. Nowadays, the expression is often used to refer to a group of people who are regarded as tiresome or difficult to deal with.

have an axe to grind

Have a private, sometimes malign, motive for doing or
being involved in something.

This expression originated in a story told by Benjamin Franklin and was used first in the USA, especially with reference to politics, but it is now in general use.

1997 - Times - I am a non-smoker and have no personal axe to grind.

the ayes have it

the affirmative votes are in the majority

Aye is an archaic or dialect word meaning YES now used in standard speech only when voting. Compare with the noes have it (at NO).

2000 - Guardian - The arguments will continue. But we think the ayes have it.